Decal removal composition

ABSTRACT

A decal removal composition which loosens the adhesive which bonds the decal to an aircraft&#39;s painted surface without adversely affecting the underlying protective paint system. The composition includes three active solvents, viz., xylene, mineral spirits and MIBK. The composition also includes thickeners and evaporation retardants as well as water mixed with a wetting agent.

STATEMENT OF GOVERNMENT INTEREST

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

CROSS-REFERENCES TO RELATED APPLICATIONS

This is a division of application Ser. No. 528,114, filed Nov. 29, 1974,now U.S. Pat. No. 3,920,472.

BACKGROUND OF THE INVENTION

This invention relates to new compositions and methods for removingresin based adhesives from aircraft surfaces. More particularly thisinvention relates to the use of such compositions and methods forremoving decals from aircraft surfaces without deleteriously affectingthe underlying paint system by dissolving the resin based adhesive whichsecures the decal to the aircraft surface.

Most, if not all, naval aircraft are provided with one or more decals,such as squadron insignia, which must be removed from time to time. Apresently used method of decal removal entails scuff sanding, sandblasting and stripping with MIL-R-81294A polyurethane and epoxy remover.The present decal remover process is not only expensive and timeconsuming but also frequently destructive of the underlying protectivepaint system. After a decal has been removed by presently employedmethods, the aircraft surface must be completely refinished with a newconversion coating, primer and topcoat. Another decal removal methodentails subjecting the decal to relatively intense heat to therebysoften the adhesive but the heat tends to scorch and burn the underlyingpaint system.

SUMMARY OF THE INVENTION

Accordingly, it is an object of this invention to provide a decalremoval composition which removes aircraft decals without adverselyaffecting the underlying paint system. It is a further object of thisinvention to provide a method of decal removal composition which is moreeffective, less expensive and less time consuming than presently usedmethods. These and other objects are accomplished as follows.

A decal removal composition comprises three active solvents, thickeners,soaps, evaporation retardants, water and wetting agents. The solventsinclude an appropriate mixture of xylene, mineral spirits and methylisobutyl ketone (MIBK). The evaporation retardants include paraffin waxwhile the thickeners include a mixture of oleic acid andmonoethanolamine with methocel added for body.

After the removal composition has been prepared, the decal is lightlyscuffed with aluminum oxide cloth and the stripper composition isthereafter liberally applied over and around the decal. After 2 hours orless the decal is loosened by the stripper composition and maythereafter be lifted from the aircraft surface with a thin stiff spatulaor other suitable means. After the decal has been removed, the affectedarea may be washed with a conventional solvent, such as that specifiedin in Federal Specification P-D-680, to remove residual decal adhesiveand spent decal removal composition.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Typical aircraft decals such as the Scotchcal 4690 Series Filmmanufactured by the Decorative Products Division of the 3M Co., aremultiply structures which include, inter alia, a thin polyester film.The decals must meet the requirements of MIL-P-38477 (USAF) PlasticMaterial, Pressure Sensitive Adhesive for Aircraft Identification andMarking. Insignia paint may be applied to one side of the decal. A thinlayer of decal adhesive is pre-coated on the other side of the decal.The decals may also have minute perforations extending through the plys.The decal adhesive is a resin based pressure sensitive adhesive whichresists moisture and commonly used solvents. The adhesive creates astrong bond between the decal and the aircraft surface after beingpressed into place. Since the edges of the decal are subject to theabrasive action of airflow during flight, washing actions, rain andother environmental factors, an edge sealer is applied in overlappingfashion to the periphery of the decal. Edge sealers must meet therequirements of MIL-P-38477; a suitable edge sealer is No. 4150 EdgeSealer provided by the 3M Co.

The decal removal (stripper) composition of the present invention isdesigned to attack and dissolve the pressure sensitive adhesive and theedge sealer. While the invention is not limited to any particular theoryas to the mechanism by which the stripping composition operates, it isbelieved that the composition operates to soften the resin basedadhesive and disrupt the bond between the adhesive and the paintedaircraft surface as well as to dissolve the adhesive itself.

The stripper composition of the present invention performs its functionwithout deleteriously affecting the underlying paint system. By paintsystem is meant weathered or aged polyurethane systems such as that setforth in Military Specification MIL-C-81773 or epoxy systems such asthat set forth in Military Specification MIL-P-22750. (The polyurethanepaint systems are normally applied to military aircraft after thesurface of the aircraft has been prepared with a conversion coating,Military Specification MIL-C-5541 and a primer, Military SpecificationMIL-P-23377).

A formulation for a preferred decal removal or stripper compositionaccording to the invention is set forth below. It is to be understoodthat this is offered by way of illustration only and is not intended inany way to limit the invention.

The stripper contains the following active ingredients between thestated ranges on a volume basis:

    ______________________________________                                        xylene                54-58%                                                  mineral spirits       10.5-11.5%                                              methyl isobutyl ketone                                                                              32-34%                                                  ______________________________________                                    

In actual practice it may be desirable to add other components to thestripper composition such as evaporation retardants, thickeners,diluents, water wetting agents and soaps (or emulsifying agents).Evaporation retardants such as paraffin wax form a thin skin across thesurface of the stripper compound after it has been applied to the decalto thereby reduce evaporation of the three active ingredients.Thickeners and soaps such as oleic acid, monoethanolomine and methylcellulose ether thickener such as "Methocel" not only provide a vehiclefor the three active ingredients but also increase the viscosity of thestripper composition so that it may more easily be applied to verticallyoriented surfaces. The water and wetting agents act as diluents.

An example of the mixture of the three active ingredients and theforegoing additional components is set forth in Table I on a parts byweight basis.

                  Table I                                                         ______________________________________                                        water                   100                                                   wetting agent            1                                                    oleic acid               15                                                   monoethanolamine         10                                                   xylene                  216 ± 4.32                                         mineral spirit           39 ± 0.20                                         paraffin wax             8                                                    methyl isobutyl ketone  120 ± 1.20                                         methyl cellulose ether thickener                                                                       2                                                    ______________________________________                                    

A particular efficacious mixture of the three active ingredients and theforegoing additional components is set forth below in Table II. (Otherquantities of the stripper composition may be made by proportionateadjustment of ingredients).

                  Table II                                                        ______________________________________                                        water                   100     mls                                           wetting agent           1.0     gms                                           oleic acid              15.0    gms                                           monoethanolamine        10.0    gms                                           xylene                  250     mls                                           mineral spirit          50      mls                                           paraffin wax            8       gms                                           methyl isobutyl ketone  150     mls                                           methyl cellulose ether thickener                                                                      2       gms                                           ______________________________________                                    

The foregoing decal removal composition is prepared by mixing theingredients while subjected to constant stirring to avoid lumping. Theingredients are mixed in the order listed in Tables I and II, however,the paraffin wax should be melted and the mineral spirits added to thewax to place the wax in suspension.

A suitable xylene is that set forth in federal specificationTT-T-916,i.e. ortho-xylene with a molecular weight of 106.16 and aspecific gravity of 0.865 at 25°C. A suitable MIBK is that set forth infederal specification TT-M-268C and having a specific gravity of 0.802at 25°C.

By wetting agent is meant a material that softens the water and causesthe water to cling to a surface. A suitable wetting agent is Aerosol 80,i.e. dihexyl ester sodium sulfosuccinic acid. By mineral spirits ismeant a petroleum distillate that will dissolve some of the resinbinders. A suitable mineral spirit is that set forth in federalspecification P-D-680 (Type II), i.e. a solvent having a boiling rangebetween 350°F and 415°F, a minimum flash point of 138°F, and an averagespecific gravity of 0.777 at 25°C.

The active ingredients of the stripper composition are the threesolvents, viz., xylene, mineral spirits, and methyl isobutyl ketone(MIBK). It has been found that the decal adhesive previously alluded tois not adequately dissolved by any of the solvents acting individually;dissolution of the adhesive is only accomplished by the three solventsacting jointly after being mixed in the proportions set forth above. Ithas also been found that MIBK acting alone will attack the paint systemapproximately 2 hours after being applied but does not attack the paintsystem when combined with xylene and mineral spirits as set forth above.

Decal removal with the stripper composition set forth above isaccomplished as follows. The decal is lightly scuffed with an aluminumoxide cloth (180 to 320 grit) or other suitable means to thereby producea more penetrable surface. Thereafter the stripper composition isdirectly applied to the scuffed decal area by brush or other suitablemeans and allowed to remain thereon for approximately 2 hours or asrequired depending upon the strength of the adhesive bond to theaircraft surface. After the decal has loosened it may be lifted off witha thin stiff spatula or similar device or the edges may be carefullylifted and the decal pulled off. After the decal has been completelyremoved, the surface may be washed with a mild solvent such as mineralspirits to remove spent stripper and residual decal adhesive.

Obviously, many modifications and variations of the present inventionare possible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

1. A composition comprising, on a volume basis:

    ______________________________________                                        xylene                54-58%                                                  mineral spirits       10.5-11.5%                                              methyl isobutyl ketone                                                                              32-34%.                                                 ______________________________________                                    


2. A decal removal composition consisting of, on a volume basis:

    ______________________________________                                        xylene                54-58%                                                  mineral spirits       10.5-11.5%                                              methyl isobutyl ketone                                                                              32-34%.                                                 ______________________________________                                    


3. A decal removal composition consisting of, on a parts by weightbasis:

    ______________________________________                                        water                   100                                                   wetting agent            1                                                    oleic acid               15                                                   monoethanolamine         10                                                   xylene                  216 ± 4.32                                         mineral spirit           39 ± 0.20                                         paraffin wax             8                                                    methyl isobutyl ketone  120 ± 1.20                                         methyl cellulose ether thickener                                                                      
 2.                                                   ______________________________________                                    